Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys

Microstructural developement during continuous cooling (0.245oC/min to 500oC/min) from the α-Ti phase region and subsequent annealing treatment, 1450oC (15minutes) 1250oC (1 hour) has been investigated using Ti-48Al, Ti-48Al- 2Cr, Ti-48Al-4Cr and Ti-48Al-8Cr (at. %) alloys. In the Ti-48Al alloys...

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Main Author:	Mohamed Jamil, Fariza
Format:	Thesis
Language:	English
Published:	2012
Subjects:	TJ Mechanical engineering and machinery
Online Access:	http://eprints.utm.my/id/eprint/28953/5/FarizaMohamedJamilMFKM2012.pdf
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id	my-utm-ep.28953
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spelling	my-utm-ep.289532018-05-27T06:39:16Z Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys 2012-01 Mohamed Jamil, Fariza TJ Mechanical engineering and machinery Microstructural developement during continuous cooling (0.245oC/min to 500oC/min) from the α-Ti phase region and subsequent annealing treatment, 1450oC (15minutes) 1250oC (1 hour) has been investigated using Ti-48Al, Ti-48Al- 2Cr, Ti-48Al-4Cr and Ti-48Al-8Cr (at. %) alloys. In the Ti-48Al alloys and Ti-48Al- 2Cr, nearly fully lamellar transform fully lamellar with the lamellar grain size and lamellar spacing decrease as the cooling rates increases. At slowest cooling rates, a small amount of Widmanstatten-lamellar structure observed appears to be intermediate between the lamellar structure. Meanwhile, addition of chromium up to 4%, at any cooling rates the lamellar grain size remain unchanged. But the formation of β phase is increases at fastest cooling rate (oil quenched). This is due to the precipitation of the β phase at grain boundaries during heat treatment and insufficient time to dissolve to α and γ phase due to fast cooling. Slowest cooling rates (furnace cooled) all β phase completely dissolved as the following transformation β α + γ α2+ γ. The study revealed at 8% of Chromium slowest and fastest cooling rates shows large portion of β phase at precipitated at grain boundaries but at intermediate cooling rates the β phases seem disappeared or dissolved. Microhardness analysis shows that several factors significantly increase the hardness value of Ti-48Al alloys which is the evolution of α2-volume fraction, high cooling rates and smallest lamellar spacing. 2012-01 Thesis http://eprints.utm.my/id/eprint/28953/ http://eprints.utm.my/id/eprint/28953/5/FarizaMohamedJamilMFKM2012.pdf application/pdf en public masters Universiti Teknologi Malaysia, Faculty of Mechanical Engineering Faculty of Mechanical Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TJ Mechanical engineering and machinery
spellingShingle	TJ Mechanical engineering and machinery Mohamed Jamil, Fariza Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys
description	Microstructural developement during continuous cooling (0.245oC/min to 500oC/min) from the α-Ti phase region and subsequent annealing treatment, 1450oC (15minutes) 1250oC (1 hour) has been investigated using Ti-48Al, Ti-48Al- 2Cr, Ti-48Al-4Cr and Ti-48Al-8Cr (at. %) alloys. In the Ti-48Al alloys and Ti-48Al- 2Cr, nearly fully lamellar transform fully lamellar with the lamellar grain size and lamellar spacing decrease as the cooling rates increases. At slowest cooling rates, a small amount of Widmanstatten-lamellar structure observed appears to be intermediate between the lamellar structure. Meanwhile, addition of chromium up to 4%, at any cooling rates the lamellar grain size remain unchanged. But the formation of β phase is increases at fastest cooling rate (oil quenched). This is due to the precipitation of the β phase at grain boundaries during heat treatment and insufficient time to dissolve to α and γ phase due to fast cooling. Slowest cooling rates (furnace cooled) all β phase completely dissolved as the following transformation β α + γ α2+ γ. The study revealed at 8% of Chromium slowest and fastest cooling rates shows large portion of β phase at precipitated at grain boundaries but at intermediate cooling rates the β phases seem disappeared or dissolved. Microhardness analysis shows that several factors significantly increase the hardness value of Ti-48Al alloys which is the evolution of α2-volume fraction, high cooling rates and smallest lamellar spacing.
format	Thesis
qualification_level	Master's degree
author	Mohamed Jamil, Fariza
author_facet	Mohamed Jamil, Fariza
author_sort	Mohamed Jamil, Fariza
title	Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys
title_short	Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys
title_full	Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys
title_fullStr	Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys
title_full_unstemmed	Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys
title_sort	effect of heat treatment on the microstructures and hardness of ti-48al-xcr alloys
granting_institution	Universiti Teknologi Malaysia, Faculty of Mechanical Engineering
granting_department	Faculty of Mechanical Engineering
publishDate	2012
url	http://eprints.utm.my/id/eprint/28953/5/FarizaMohamedJamilMFKM2012.pdf
_version_	1747815699688980480

Effect of heat treatment on the microstructures and hardness of Ti-48Al-xCr alloys

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